Wladyslaw W. Szymanski

Nano ES GEMMA and PDMA, new tools for the analysis of nanobioparticles—Protein complexes, lipoparticles, and viruses

Differential mobility analysis (DMA) is a technique suited for size analysis as well as preparative collection of airborne nanosized airborne particles. In the recent decade, the analysis of intact viruses, proteins, DNA fragments, polymers, and inorganic nanoparticles was possible when combining this method with a nano-electrospray charge-reduction source for producing aerosols from a sample solution/suspensions. Mass analysis of high molecular weight noncovalent complexes is also possible with this methodology due to the linear correlation of the electrophoretic mobility diameter and the molecular mass. In this work, we present the analysis (size and molecular mass) of high molecular weight multimers (noncovalent functional homocomplex) of Jack bean urease in a mass range from 275 kDa up to 2.5 MDa, with mainly present tri- and hexamers but also higher oligomers of the 91 kDa monomer subunit. In a second experiment, the size analysis of intact very-low-density (∼35 nm), low-density (∼22 nm) and high-density lipoparticles (∼10 nm), which are heterocomplexes consisting of cholesterol, lipids, and proteins in different ratios, is presented. Results from mobility analysis were in excellent agreement with particle diameters found in literature. The last presented experiment demonstrates size analysis of a rod-like virus and selective sampling of a selected size fraction of electrosprayed, singly-charged tobacco mosaic virus particles. Sampling and subsequent transmission electron microscopic investigations of a specific size fraction (40 nm electrophoretic mobility diameter) revealed the folding of virus particles during the electrospray and charge reduction (electrical stress) as well as solvent evaporation (mechanical stress) process, leading to an observed geometry of 150 (length) × 35 (width) nm (average cylindrical geometry of unsprayed intact virus 300 × 18 nm).

Intercomparison of number concentration measurements by various aerosol particle counters

Abstract Total aerosol particle number concentrations, as measured by means of 16 different measurement systems, have been quantitatively compared during an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (ICCP-IUGG). The range of measuring instruments includes Pollak counters (PCO) in use already for several decades, presently available commercial particle counters, as well as laboratory prototypes. The operation of the instruments considered was based on different measurement principles: (1) adiabatic expansion condensation particle counter, (2) flow diffusion condensation particle counter, (3) turbulent mixing condensation particle counter, (4) laser optical particle counter, and (5) electrostatic particle measurement system. Well-defined test aerosols with various chemical compositions were considered: DEHS, sodium chloride, silver, hydrocarbons, and tungsten oxide. The test aerosols were nearly monodispersed with mean particle diameters between 4 and 520 nm, the particle number concentrations were varied over a range from about 4×10 1 to 7×10 6 cm −3 . A few measurements were performed with two-component aerosol mixtures. For simultaneous concentration measurements, the various instruments considered were operated under steady state conditions in a linear flow system. A series of at least 10 single concentration measurements was performed by each individual instrument at each set of test aerosol parameters. The average of the concentration data measured by the various instruments was defined as a common reference. The number concentrations obtained from the various instruments typically agreed within a factor of about two over the entire concentration range considered. The agreement of the measured concentrations is notable considering the various different measurement principles applied in this study, and particularly in view of the broad range of measurement instruments used. Significant deviations and nonlinear response were observed only in a few cases and are possibly related to calibration errors. For certain conditions, a dependence of aerosol counter response on particle composition has been found. The scatter of the number concentrations obtained from each individual instrument during measurements with constant test aerosol typically did not exceed 20% to 25%. At concentrations below 10 3 cm −3 , however, several of the instruments, including electrostatic particle measurement systems, tend to show increased experimental scatter.

A new method for the simultaneous measurement of aerosol particle size, complex refractive index and particle density

Particle size measurement by means of optical spectrometry of single particles depends substantially on the angular range of light scattering and the refractive index of the particle. Knowledge of the latter determines implicitly the accuracy of measurement. In contrast to commonly used instrumental systems the configuration of the design concept presented here consists of two laser illumination sources with different wavelengths and four angular ranges for the collection of scattered light. As a result a set of four independent pulses from each measured particle can be obtained allowing simultaneous assessment of particle size and its complex refractive index. Based on the Mie theory of light scattering, light collection angles yielding a single-valued aerosol size measurement were identified and used to design a new optical system. Based on the modelling of the performance for an assumed instrumental arrangement the sizing errors were found to be about 2%. The accuracy of assessment of the complex index of refraction was found to be of the order of 10% over the range of particle diameters investigated (0.1-10 µm). The theoretical results show clearly the capability of this novel instrumental design for the measurement of aerosol particle sizes, their density and optical properties. Based on these model calculations an experimental set-up is under construction.

Particle size dependent response of aerosol counters

During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions. The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the

Gas-phase electrophoretic molecular mobility analysis of size and stoichiometry of complexes of a common cold virus with antibody and soluble receptor molecules.

Attachment of a nonaggregating monoclonal antibody and of a soluble recombinant receptor molecule to the icosahedral nonenveloped human rhinovirus serotype 2 was studied with a nanoelectrospray ionization gas-phase electrophoretic molecular mobility analyzer (nESI-GEMMA). The virus mass, as determined via nESI-GEMMA, was within instrument accuracy (+/-6%) close to the theoretical value (8 x 10(6) Da) calculated from the sum of all constituents of one virus particle (60 copies of each of the four viral capsid proteins, the RNA genome, and one copy of the RNA-linked protein VpG). The formation of virus-antibody complexes of different stoichiometries (up to a mass 12.5 x 10(6) Da corresponding to 30 attached antibodies) and virus-receptor complexes (up to a mass 8.8 x 10(6) Da corresponding to 12 attached receptor molecules) was monitored. Via the volume derived from the electrophoretic mobility diameter (EMD), the stoichiometry of the HRV complexes was calculated. The accuracy of the EMD was within +/-0.5 nm, which corresponds to an accuracy of +/-4 antibodies and +/-5 receptor molecules in the respective complexes. For the first time, we here demonstrate the use of nESI-GEMMA for the analysis of the size and stoichiometry of biomolecules in high-order complexes in real time under normal pressure conditions.

Quantification of scattering corrections to the Beer-Lambert law for transmittance measurements in turbid media

We present a modelled approach of scattering contribution to the radiation transmission through a scattering medium, such as an aerosol, yielding a correction term to the Lambert-Beer law. The correction is essential because a certain amount of the forward scattered light flux is always overlaid on the transmitted radiation. Hence it enters together with the attenuated beam into the finite aperture of any detector system and therefore constitutes a potential problem in the inversion of measured data. This correction depends not only on the geometry of the measuring system but also substantially on the optical depth of the medium. We discuss the numerical analysis of the magnitude and functional behaviour of the scattering correction for a number of important measuring parameters and we give a simple approximation for the determination of the range of applicability of the scattering correction for single scattering conditions. Finally, we show that the derived expressions yield useful values of optical depths at which non-negligible multiple scattering effects occur.

Measurements of Kelvin-equivalent size distributions of well-defined aerosols with particle diameters > 13 nm

During the 1979 workshop of the working group on ultrafine aerosols, different experimental techniques for measuring the number concentration and size of ultrafine aerosol particles were compared. In the present paper we report on a comparison of different particle size measuring techniques for ultrafine aerosols. Well-defined monodisperse aerosols with electrical mobility particle diameters ranging from 13 to 100 nm were generated using an electrical aerosol classifier. Kelvin-equivalent size distributions of these aerosols were determined by means of a process-controlled expansion chamber, the size-analyzing nuclei counter (SANC). To this end the considered aerosol was humidified and the number concentration of the droplets growing in the expansion chamber was measured for stepwise increase in supersaturation. At a quite well defined critical supersaturation, a significant increase in the measured droplet concentration, and thus the onset of heterogeneous nucleation, was observed. By means of the Kelvin...

Detection of aluminum particles during the chemical vapor deposition of aluminum films using tertiaryamine complexes of alane (AlH3)

Two methods of analyzing particles were interfaced to a low pressure chemical vapor deposition (CVD) reactor to evaluate whether or not particles were formed in the gas phase during the growth of aluminum films using tertiaryamine complexes of alane. A laser light scattering particle counter was used to detect large (>200 nm) particles in real time and established that the appearance of particles corresponded to the flow of precursor into the CVD reactor. A particle impaction system was used to collect particles (>20 nm) for analysis using analytical electron microscopy and electron diffraction. This established that the particles were crystalline aluminum and that the particle sizes ranged from 20–700 nm. The median size was 85 nm.

Absolute aerosol number concentration measurement by simultaneous observation of extinction and scattered light

Abstract A quantitative measurement of laser light extinction during particle growth in an expansion chamber of a condensation nuclei counter was performed. The attenuated light flux and the light flux scattered at a selectable scattering angle are monitored simultaneously during the particle growth process. From the transmitted light flux vs time the light extinction during particle growth can be determined quantitatively. The experimental scattered light flux vs time allows a precise determination of particle sizes at various times during particle growth. Knowing the actual particle size, the light attenuation obtained from the transmitted light flux allows a direct, quantitative determination of particle number concentration without referring to any calibration of the apparatus. Measurements have been performed over a range of aerosol number concentrations and compared with two different techniques. The results obtained show that the simultaneous observation of transmitted and scattered light permits an absolute aerosol number concentration measurement.

Comparison of various nano-differential mobility analysers (nDMAs) applying globular proteins

The demand for analysis of nanosized particles and assemblies of biologic and inorganic origin has increased in the recent decade together with the growing development of biotechnology and nanotechnology. Recent developments of electrostatic differential mobility analysis (DMA) provide an excellent characterization tool in the nanometer size range. With an increasing number of available nano-DMA (nDMA) systems, the question of data comparability and implementation of possible calibration procedures arise. Here we present analysis of proteins in a range between 3 nm (5.7 kDa) and 15 nm (660 kDa) with five different nDMA systems. Results show differences in the obtained sizes up to 15% between different nDMA systems, which consequently leads to the conclusion that a calibration procedure for each nDMA is necessary when applying such systems for the analysis of nanoparticles with respect to size and molecular mass.